Bilayer Isotropic Thermal Cloak

Invisibility has attracted intensive research in various communities, e.g., optics, electromagnetics, acoustics, thermodynamics, etc. However, the most of them have only been experimentally achieved by virtue of simplified approaches due to their inhomogeneous and extreme parameters imposed by transformation-optic method, and usually require challenging realization with metamaterials. In this paper, we demonstrate an advanced bilayer thermal cloak with naturally available materials first time. This scheme, directly from thermal conduction equation, has been validated as an exact cloak rather than a reduced one, and we experimentally confirmed its perfect performance (heat-front maintenance and heat protection) in an actual setup. The proposed scheme may open a new avenue to control the diffusive heat flow in ways inconceivable with phonons.